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Lucene example source code file (CompressionTools.java)

This example Lucene source code file (CompressionTools.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

bytearrayoutputstream, bytearrayoutputstream, compressiontools, dataformatexception, dataformatexception, deflater, deflater, inflater, inflater, io, string, zip

The Lucene CompressionTools.java source code

package org.apache.lucene.document;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.util.zip.Deflater;
import java.util.zip.Inflater;
import java.util.zip.DataFormatException;
import java.io.ByteArrayOutputStream;
import org.apache.lucene.util.UnicodeUtil;

/** Simple utility class providing static methods to
 *  compress and decompress binary data for stored fields.
 *  This class uses java.util.zip.Deflater and Inflater
 *  classes to compress and decompress.
 */

public class CompressionTools {

  // Export only static methods
  private CompressionTools() {}

  /** Compresses the specified byte range using the
   *  specified compressionLevel (constants are defined in
   *  java.util.zip.Deflater). */
  public static byte[] compress(byte[] value, int offset, int length, int compressionLevel) {

    /* Create an expandable byte array to hold the compressed data.
     * You cannot use an array that's the same size as the orginal because
     * there is no guarantee that the compressed data will be smaller than
     * the uncompressed data. */
    ByteArrayOutputStream bos = new ByteArrayOutputStream(length);

    Deflater compressor = new Deflater();

    try {
      compressor.setLevel(compressionLevel);
      compressor.setInput(value, offset, length);
      compressor.finish();

      // Compress the data
      final byte[] buf = new byte[1024];
      while (!compressor.finished()) {
        int count = compressor.deflate(buf);
        bos.write(buf, 0, count);
      }
    } finally {
      compressor.end();
    }

    return bos.toByteArray();
  }

  /** Compresses the specified byte range, with default BEST_COMPRESSION level */
  public static byte[] compress(byte[] value, int offset, int length) {
    return compress(value, offset, length, Deflater.BEST_COMPRESSION);
  }
  
  /** Compresses all bytes in the array, with default BEST_COMPRESSION level */
  public static byte[] compress(byte[] value) {
    return compress(value, 0, value.length, Deflater.BEST_COMPRESSION);
  }

  /** Compresses the String value, with default BEST_COMPRESSION level */
  public static byte[] compressString(String value) {
    return compressString(value, Deflater.BEST_COMPRESSION);
  }

  /** Compresses the String value using the specified
   *  compressionLevel (constants are defined in
   *  java.util.zip.Deflater). */
  public static byte[] compressString(String value, int compressionLevel) {
    UnicodeUtil.UTF8Result result = new UnicodeUtil.UTF8Result();
    UnicodeUtil.UTF16toUTF8(value, 0, value.length(), result);
    return compress(result.result, 0, result.length, compressionLevel);
  }

  /** Decompress the byte array previously returned by
   *  compress */
  public static byte[] decompress(byte[] value) throws DataFormatException {
    // Create an expandable byte array to hold the decompressed data
    ByteArrayOutputStream bos = new ByteArrayOutputStream(value.length);

    Inflater decompressor = new Inflater();

    try {
      decompressor.setInput(value);

      // Decompress the data
      final byte[] buf = new byte[1024];
      while (!decompressor.finished()) {
        int count = decompressor.inflate(buf);
        bos.write(buf, 0, count);
      }
    } finally {  
      decompressor.end();
    }
    
    return bos.toByteArray();
  }

  /** Decompress the byte array previously returned by
   *  compressString back into a String */
  public static String decompressString(byte[] value) throws DataFormatException {
    UnicodeUtil.UTF16Result result = new UnicodeUtil.UTF16Result();
    final byte[] bytes = decompress(value);
    UnicodeUtil.UTF8toUTF16(bytes, 0, bytes.length, result);
    return new String(result.result, 0, result.length);
  }
}

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